Verses with the word leaven in the Old Testament (9 verses):

Exodus 12:15
Seven days shall ye eat unleavened bread; even the first day ye shall put away leaven out of your houses: for whosoever eateth leavened bread from the first day until the seventh day, that soul shall be cut off from Israel.

Exodus 12:19
Seven days shall there be no leaven found in your houses: for whosoever eateth that which is leavened, even that soul shall be cut off from the congregation of Israel, whether he be a stranger, or born in the land.

Exodus 13:7
Unleavened bread shall be eaten seven days; and there shall no leavened bread be seen with thee, neither shall there be leaven seen with thee in all thy quarters.

Exodus 34:25
Thou shalt not offer the blood of my sacrifice with leaven; neither shall the sacrifice of the feast of the passover be left unto the morning.

Leviticus 2:11
No meat offering, which ye shall bring unto the LORD, shall be made with leaven: for ye shall burn no leaven, nor any honey, in any offering of the LORD made by fire.

Leviticus 6:17
It shall not be baken with leaven. I have given it unto them for their portion of my offerings made by fire; it is most holy, as is the sin offering, and as the trespass offering.

Leviticus 10:12
And Moses spake unto Aaron, and unto Eleazar and unto Ithamar, his sons that were left, Take the meat offering that remaineth of the offerings of the LORD made by fire, and eat it without leaven beside the altar: for it is most holy:

Leviticus 23:17
Ye shall bring out of your habitations two wave loaves of two tenth deals; they shall be of fine flour; they shall be baken with leaven; they are the firstfruits unto the LORD.

Amos 4:5
And offer a sacrifice of thanksgiving with leaven, and proclaim and publish the free offerings: for this liketh you, O ye children of Israel, saith the Lord GOD.